The objective of the study is to evaluate recombinant tissue plasminogen activator (rtPA) for treatment of acute deep vein thrombosis of the lower extremity. The study is designed to evaluate efficacy, safety, and cost of this form of treatment for restoration of venous function in the lower extremity. Eight patients have been treated. All except one patient had significant improvement. Only two patients have had evidence of small pulmonary emboli during treatment, detected on ventilation perfusion lung scans that are obtained in all patients accepted into the protocol. None of these patients were clinically symptomatic. One patient developed a non-life-threatening biceps hematoma probably induced by automatic blood pressure monitoring during the rtPA treatment. No other complications have occurred. Preliminary results have been submitted for publication in a case report for JAMA, and in an article submitted to the American Journal of Medicine.